Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Semiconductor devices perform a wide range of functions such as analog and digital signal processing, sensors, transmitting and receiving electromagnetic signals, controlling electronic devices, power management, and audio/video signal processing. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, diodes, rectifiers, thyristors, and power metal-oxide-semiconductor field-effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, application specific integrated circuits (ASIC), power conversion, standard logic, amplifiers, clock management, memory, interface circuits, and other signal processing circuits.
A semiconductor wafer includes a base substrate material and plurality of semiconductor die formed on an active surface of the wafer separated by a saw street. FIG. 1a shows a conventional semiconductor wafer 10 with base substrate material 12, active surface 14, and back surface 16.
Many applications require the semiconductor die to be reduced in height or thickness to minimize the size of the semiconductor package. FIG. 1b shows a grinding operation with grinder or grinding wheel 20 removing a portion of back surface 16 of semiconductor wafer 10 and reducing the thickness of the semiconductor wafer to about 100 micrometers (μm). Grinding wheel 20 is controlled to leave edge support ring 22 of base substrate material 12 around a perimeter of semiconductor wafer 10 for structural support. Grinding wheel 20 reduces the thickness of semiconductor wafer 10 in an interior region or wafer grinding area 24 of the wafer within edge support ring 22. FIG. 1c shows a top view of grinding wheel 20 removing a portion of back surface 16 of semiconductor wafer 10 and reducing the thickness or height of the semiconductor die in grinding area 24, while leaving edge support ring 22 of base substrate material 12 around a perimeter of semiconductor wafer 10. The height of edge support ring 22 is greater than the post-grinding thickness of semiconductor wafer 10 to maintain structural integrity of the thinner semiconductor wafer for wafer handling and manufacturing processes. The width of edge support ring 22 is symmetrical around semiconductor wafer 10, with a typical width W22 of 3.0 millimeters (mm) from inner wall 26 to outer edge 28 of the wafer.
Semiconductor wafer 10 also includes a wafer scribe identification mark 30 on active surface 14 near an edge of semiconductor wafer 10, proximate to orientation notch 32, as shown in top view of FIG. 1d. Wafer scribe mark 30 is laser inscribed with a unique identifier of semiconductor wafer 10. The laser cuts into active surface 14 within the wafer scribe ID region with a plurality of ID dots to mark the unique wafer identifier number or code. The depth of laser ID dots is 45 μm±15 μm, or typically about 35 μm. Accordingly, certain portions of base substrate material 12 within wafer scribe mark 30 have reduced thickness due to the laser marking.
To maximize the yield of the semiconductor die from semiconductor wafer 10, grinding area 24 is made as large as possible, while leaving a width and height of edge support ring 22 sufficient to maintain structural integrity of the semiconductor wafer for wafer handling and manufacturing processes. The vertical projection of grinding area 24 in back surface 16 overlaps wafer scribe mark 30 in active surface 14. A portion of wafer scribe mark 30 is disposed on edge support ring 22, and a portion of the wafer scribe mark is disposed within the vertical projection of grinding area 24, i.e., on an area of active surface 14 opposite the grinding area. In some cases, grinding area 24 extends to the depth of the laser ID dots in wafer scribe mark 30 leaving an opening completely through base substrate material 12, particularly when semiconductor wafer is thinned to less than 40 μm. In other cases, grinding area 24 extends almost to the depth of the laser ID dots in wafer scribe mark 30 with any remaining thickness of the base substrate material 12 between the laser ID dots and grinding area being susceptible to defects. In other words, grinding back surface 16 to a point at or near the depth of the laser ID dots creates holes or stress concentration points, which can lead to breakage of semiconductor wafer 10 during subsequent manufacturing processes.